The present invention relates to a blowing apparatus.
In recent years, high-density packaging of electric circuits has been increasingly used in correspondence with miniaturization and electronization of appliances. In association with this, exothermic density of such electronic appliances also increases, so that a blowing apparatus has been used for cooling the appliances.
In addition, for the purpose of reducing the cost of the appliance, there is a strong demand for reducing the cost of the blowing apparatus used in such an appliance.
As shown in FIG. 12, in a conventional blowing apparatus, a circular wall 2 is formed at a distance from a blade end of a fan 1, and under the blowing condition where a motor portion 3 is energized, the axial fan 1 rotates about a shaft 4 to generate an air flow 5 directed toward the discharge side from the suction side.
However, in the above blowing condition, the speed of the air flow becomes high at the back pressure side of the blade end, so that a low energy area is generated on the rear edge side of blade where the air flow is converted to the pressure energy under the influence of the secondary flow between blades. This area is easy to be damaged and most likely to cause separation of flow, so that there arises a problem that the air flow is separated from the blade surface, causing generation of vortex in the separation area, and which vortex increases the turbulent flow noise and deteriorates the noise level and air capacity-static pressure characteristics.
This phenomenon is frequently observed particularly in such a situation that when flow resistance (system impedance) is exerted on the discharge flow side, generation of leak vortex at the blade end increases so that the fan exhibits a stalling state.
In consideration of the above-described problems, it is an object of the present invention to provide a blowing apparatus exerting the performance which remarkably overcomes that of the conventional blowing apparatus, as well as having better productivity than the conventional blowing apparatus and thus having excellent cost performance.
A blowing apparatus according to the present invention comprises a circular wall formed at a distance from a blade end of a fan, the circular wall having a first region where an inner diameter is partially enlarged so that a clearance with the blade end on a suction side becomes substantially wide, and a second region where a clearance with the blade end is made narrow, wherein a terminal end of the second region is extended halfway on a discharge side, and an air pocket portion (11) having a certain capacity and opening toward the discharge side is formed between an outer circumference of the circular wall and an outer peripheral portion of the housing, thereby improving the characteristics of the blowing apparatus.
According to the present invention, it is possible to improve the characteristics of the blowing apparatus, as well as it is possible to improve the cost performance of the blowing apparatus by increasing productivity and realizing cost reduction.
In the first aspect, the present invention provides a blowing apparatus formed with a circular wall at a distance from a blade end of a fan and having a housing in which the circular wall and a boss portion to which a motor is to be fixed are integrally formed, wherein a terminal end of the circular wall is extended halfway on a discharge side and an air pocket portion having a certain capacity and opening toward the discharge side is formed between an outer circumference of the circular wall and an outer peripheral portion of the housing, so that it is possible to reduce noise and reduce production cost of the blowing apparatus.
Furthermore, with the blowing apparatus wherein the circular wall has a first region where the inner diameter is partially enlarged so that a clearance with the blade end becomes substantially wide on a suction side, and a second region where a clearance with the blade end is made narrower, it is possible to improve the blowing characteristic of the blowing apparatus.
Furthermore, with the blowing apparatus wherein a boss portion of the housing is connected to the circular wall and is not directly fixed to the outer peripheral portion of the housing or to an attachment hole portion, it is possible to reduce noise and oscillation of a machine under the condition that the blowing apparatus is attached to the machine.
In the second aspect, the present invention provides a blowing apparatus, wherein when defining total mass of a motor and fan as m (kg), spring constant between a boss portion and an attachment portion as k (N/m), and rotation number of motor as N (1/s), the housing is set so as to satisfy the following relation ship:   N   greater than             1              2        ⁢        π              ⁢                  k        m            
It goes without saying that the second aspect is effectively combined so as to realize the effect of the first aspect of the invention.
In the third aspect, the present invention provides a blowing apparatus formed with a circular wall at a distance from a blade end of a fan and having a housing in which the circular wall and a boss portion to which a motor is to be fixed are integrally formed, wherein the circular wall is comprised of a first region where the inner diameter is partially enlarged so that a clearance with the blade end on the suction side becomes substantially wide, and a second region where the clearance with the blade end is made narrow, wherein the terminal end of the second region is extended halfway on the discharge side, an air pocket portion having a certain capacity and opening toward the discharge side is formed between the outer circumference of the circular wall and the outer peripheral portion of the housing, and the circular wall is formed with a slit allowing air communication between the inner circumference of the circular wall and the air pocket portion, so that it is possible to improve the blowing characteristics under the condition of relatively high static pressure.
Furthermore, by forming the housing by using a mold composed of only an upper and a lower cores, it is possible to realize improvement of productivity and cost reduction.